High powered horn antennas, such as those used in satellite communications, can produce a focused high flux density that creates challenges for testing the communication electronics attached to a horn antenna. To test attached electronics, one typical configuration includes a Radio Frequency (RF) absorber backed by an actively cooled aluminum plate positioned in front of the horn antenna. A thin aluminum shroud surrounding the space between the absorber and the horn antenna can be added to create a Field Aperture Load (FAL) configuration. Limits on the absorption and cooling rate of the FAL configuration limit the maximum allowable flux density at the absorber pad. To reduce the flux density at the absorber pad, the absorber pad can be moved farther from the horn antenna such that the energy emitted from the horn is more diffuse and has a sufficiently low maximum flux density at the absorber. As the absorber pad moves further from the horn, the entire FAL, including the aluminum shroud, must grow. However, large test configurations can create increased costs and other challenges, especially during Spacecraft Thermal Vacuum (SCTV) testing, which requires an entire test configuration to fit within a vacuum chamber. Large vacuum chamber testing facilities are generally expensive with limited schedule availability.
Existing solutions have additionally involved the use of air links including probe antennas at some distance in front of the antenna under test. In some cases they have been installed at the reflector focal point to quantitatively couple RF to the satellite. This has required the use of large vacuum chambers, with limited availability, and expensive supporting structure with excessive setup time. Control of reflections causing multipath or in-band ripple is also a major issue with air links.
Another solution is the recently developed “Field Aperture Load Coupler” described in co-pending U.S. patent application Ser. No. 14/273,329, which uses a waveguide coupled reduced radiating aperture with integrated directional electric field probe (E-probe) coupler. The advantage of this method is the reduced radiating aperture spreads the radiated transmit flux over a broader area such that shorter distance to the absorber is tolerated without overheating. The use of the directional coupler allows testing in a partially reflective environment. The drawback of this method is limited power handling due to the thermal constraints and expense of the E-probe directional coupler components.